Cellular polyurethane elastomers

ABSTRACT

Cellular Polyurethane elastomer which is produced by reacting: 
     (a) an isocyanate component which includes methylenebis(phenyl isocyanate) (MDI) and/or tolylene diisocyante (TDI), in monomeric form or as liquefied prepolymer with 
     (b) compounds which at least two isocyanate-reactive hydrogen atoms and 
     (c) 4,4&#39;-methylenebis(3-chloro-2,6-dialylaniline) or a mixture of 4,4&#39;-methylenebis-(3-chloro-2,6-dialyaniline) with one or more aromatic, aliphatic or cycloaliphatic diamines as chain extending agent, if desired with further polyol, and 
     (d) a blowing agent in the presence of the usual catalysts and, if desired, other additives.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to cellular polyurethane elastomers, in particularthose which can be subjected to high dynamic stresses.

2. Background Art

High requirements are placed upon the materials of cellular polyurethaneelastomers applied, for example, in passenger or freight vehiclespringing systems or in buffer and bumper systems subject to highdynamic stresses. Cellular polyurethane elastomers based onmethylenebis-(phenyl isocyanate) (MDI) or tolylene diisocyanate (TDI)have hitherto not been able to fulfil these high requirements and havetherefore so far been used for applications subject to lower dynamicstresses. The chain extending agents used in these systems are usuallyglycols, in particular butanediols. The resultant hard polyurethanesegments have a melting range from about 180° to 200° C., and for casesof high dynamic or thermal stress this markedly impairs the mechanicalproperties of the products produced therefrom. The standard forapplications involving high dynamic stresses has hitherto been cellularpolyurethane elastomers based on naphthylene diisocyanate (NDI) andknown as "Vulkollan". These cellular polyurethane elastomers show goodbehavior under dynamic stress, but they have the disadvantage that theprepolymers are not stable when stored (cf. Kunststoff Taschenbuch[Plastics Handbook], 24th edition, Carl Hanser Verlag, Munich, 1989, pp.436ff.). The consequence for the final producer is therefore that onlyin-line production is possible, the prepolymer being convertedimmediately into the finished part. NDI-containing products also differfrom industrially produced MDI products in having a significantly higherprice level.

BROAD DESCRIPTION OF THE INVENTION

It was therefore the object of the invention to develop cellularpolyurethane elastomers which utilize the advantageous properties ofmethylenebis(phenyl isocyanate) (MDI) and tolylene diisocyanate (TDI)with respect to storage capability of the prepolymers and toavailability and advantageous price, and which in their materialproperties achieve the requirements for applications involving highdynamic stresses.

The object was achieved with cellular polyurethane elastomers accordingto of the invention.

According to the invention, the cellular polyurethane elastomer may beproduced by reacting

a) an isocyanate component which includes methylenebis(phenylisocyanate) (MDI) and/or tolylene diisocyanate (TDI), in monomeric formor as liquefied prepolymer with

b) compounds with at least two isocyanate-reactive hydrogen atoms and

c) 4,4'-methylenebis(3-chloro-2,6-dialkylaniline) or a mixture of4,4'-methylenebis(3-chloro-2,6-dialkylaniline) with one or morearomatic, aliphatic or cycloaliphatic diamines as chain extending agent,if desired with further polyol, and

d) a blowing agent and, if desired, in the presence of the usualcatalysts and other additives.

The isocyanate component MDI is generally monomeric4,4'-methylenebis(phenyl isocyanate) or pre-polymers thereof liquefiedwith small proportions of polyol. However, this term also includes anMDI which expediently contains proportions of up to 30% by weight of theisomeric 2,4'-methylenebis(phenyl isocyanate). Mixtures of MDI withother polyisocyanates, for example with tolylene diisocyanate (TDI) orwith other industrially obtainable diisocyanates, for examplehexamethylene diisocyanate or isophorone diisocyanate, are likewiseincluded in this term. It is, however, also possible to obtaincommercially, and use, the MDI in the form of a prepolymer with aparticular NCO content, for example under the name Vibrathane®.

The tolylene diisocyanate is generally either the isomerically pure 2,4-or 2,6-isomer or any desired mixture of these isomers with one another.An isomer mixture of the 2,4- and 2,6-isomers in a ratio of 80:20 or65:35 is, for example, known and obtainable in industrial quantities. Itis, however, also possible to obtain commercially, and use, the TDI inthe form of a prepolymer with a particular NCO content, for exampleunder the name Vibrathane®.

Examples of suitable compounds with at least two polyisocyanate-reactivehydrogen atoms are in particular polyols, for example polyether polyols,polyester polyols or other polyols (e.g. polycaprolactones) with amolecular weight range of from 500 to 10,000, preferably from 800 to5000. Examples listed are the polytetramethylene ether glycols marketedunder the trade mark Terathane® (Du Pont), the polyether polyolsmarketed under the trade mark Acclaim® (Arco), the polyester diolsmarketed under the trade mark Daltorez® (ICI) or Desmophen® (Bayer) orthe polyols containing carbonate groups and marketed under thedesignation PolyTHF/CD(BASF).

It is expedient for the alkyl group in the4,4'-methylenebis(3-chloro-2,6-dialkylaniline) to be a methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl or tert-butyl group, butparticularly preferably an ethyl group. The preparation of these4,4'-methylenebis(3-chloro-2,6-dialkylanilines) used as chain extendingagents is described in detail in European Patent No. 220,541. The4,4'-methylenebis(3-chloro-2,6-dialkylaniline) may be used either aloneor as a constituent of a mixture with other aromatic, aliphatic orcycloaliphatic amines, for example with the known compounds MOCA,dimethylthio-toluenediamine or with triamines or diamines based onpolypropylene glycol. The chain extending agent is advantageously usedtogether with a polyol. Suitable polyols here are those mentioned above,for example polyether polyols, polyester polyols or other polyols (e.g.polycaprolactones) with a molecular weight range of from 500 to 10,000,preferably from 800 to 5000. The polyol component is expediently used ina molar ratio, based on the chain extending agent, of from 0.1 to 10,preferably from 0.5 to 5.

The blowing agent used is preferably water or a commercially availablewater-based blowing agent with added dispersing agent, for exampleBayer's SM® blowing agent. However, it is also possible to use other, orunder some circumstances additional, blowing agents, e.g. blowing agentswith a physical action and based on hydrocarbons or else halogenatedhydrocarbons. The blowing agent is expediently used in amounts of from0.1 to 9 mol, based on 1 mol of chain extending agent.

It is also possible to use the usual catalysts, for exampletetramethylbutanediamine (TMBDA), diazabicyclooctane (DABCO), dibutyltindilaurate (DBTC) or organic heavy metal compounds, individually or incombinations. Examples of usual additives are plasticizers, stabilizers,flame retardants and fillers (cf., for example, Kunststoff Taschenbuch[Plastics Handbook], 24th edition, Carl Hanser Verlag, Munich, 1989, p.430).

The components may expediently be processed via the one-shot process orthe prepolymer process, preferably via the prepolymer process (cf. forexample, Kunststoff Taschenbuch [Plastics Handbook], 24th edition, CarlHanser Verlag, Munich, 1989, pp. 429 ff.).

In the prepolymer process it is expedient to react the components

a) methylenebis(phenyl isocyanate) (MDI) or tolylene diisocyanate (TDI)with the component

b) compounds with at least two isocyanate-reactive hydrogen atoms togive a prepolymer which has a content of from 2 to 28% by weight of freeisocyanate groups.

MDI and TDI prepolymers are available commercially with various NCOcontents, for example under the trade mark Vibrathane® (Uniroyal).

The "polyol component" is expediently composed of the component

c) 4,4'-methylenebis(3-chloro-2,6-dialkylaniline) or a mixture of4,4'-methylenebis(3-chloro-2,6-dialkylaniline) with one or morearomatic, aliphatic or cycloaliphatic diamines as chain extending agentand

d) the blowing agent and, if desired, the usual catalysts and otheradditives.

In the one-shot process, it is expedient to react the "isocyanatecomponent"

a) methylenebis(phenyl isocyanate) (MDI) (modified, if desired, withsmall amounts of a polyol in such a way that a liquid component isproduced at low temperatures) or tolylene diisocyanate (TDI) with the"polyol component" composed expediently of the components

b) compounds with at least two isocyanate-reactive hydrogen atoms aprepolymer is prepared [lacuna] which has a content of from 2 to 30% byweight of free isocyanate groups.

c) 4,4'-methylenebis(3-chloro-2,6-dialkylaniline) or a mixture of4,4'-methylenebis(3-chloro-2,6-dialkylaniline) with one or morearomatic, aliphatic or cycloaliphatic diamines as chain is extendingagent and

d) the blowing agent and, if desired, the usual catalysts and otheradditives.

The processing of the prepolymer component or of the isocyanatecomponent with the polyol component to give the cellular polyurethaneelastomer takes place in a manner known, preferably in a casting processin closed molds (cf., for example, Kunststoff Taschenbuch [PlasticsHandbook], 24th edition, Carl Hanser Verlag, Munich, 1989, pp. 436ff.).The cellular polyurethane elastomers produced according to the inventionare distinguished by high dynamic stress resistance and heat resistanceand are therefore particularly suitable for use in moldings subject tohigh dynamic stresses and in systems for the decoupling of vibrations inmotor vehicles and machines. Examples are resilient elements in shockabsorbers for passenger or freight vehicles or buffer and bumpersystems.

DETAILED DESCRIPTION OF THE INVENTION EXAMPLES (MDI)

Prepolymer 1

1250 g (5 mol) of 4,4'-methylenebis(phenylisocyanate) (MDI) were meltedat 60° C. and, with stirring and exclusion of atmospheric moisture,mixed within a period of 15 minutes with 1000 g (0.5 mol) ofpolycaprolactone (Capa® 225 from Interox) which had been melted at 60°C. Stirring was continued for a further hour at 80° C., giving 2250 g ofa prepolymer which was liquid at 35° C. and had a NCO content of 16.8%.

Prepolymer 2

Commercially available Vibrathane® 8010 from Uniroyal. (MDI prepolymerwith an NCO content of 9.26%).

Prepolymer 3

Commercially available Vibrathane® B625 from Uniroyal. (PTMEG-MDIprepolymer with an NCO content of 6.28%).

Polyol Component 1

2000 g (1 mol) of polycaprolactone diol (Capa® 220 from Interox) at 60°C. were mixed with 380 g (1 mol) of molten4,4'-methylenebis(3-chloro-2,6-diethylaniline) (LONZACURE® MCDEA fromLONZA AG). The following additions were then incorporated:

    ______________________________________                                        27 g (1.5 mol) of water                                                       ______________________________________                                        Catalysts:   6 g of Dabco ® 1028                                                                      (Air Products)                                       1 g of Dabco ® solid (Air Products)                                       5 g of Dabco ® BL17 (Air Products)                                       Cell stabilizer: 20 g of LK221 (Air Products)                               ______________________________________                                    

This gives a polyol/diamine/water component with an equivalent weight of348.

Polyol Component 2

The 27 g (1.5 mol) of water in polyol component 1 were replaced by 36 g(1 mol) of SM® (50% strength water/sulphonate mixture from Bayer,Leverkusen). The formulation remaining otherwise identical, this gives apolyol/diamine/water mixture with an equivalent weight of 406.

Polyol Component 3

2000 g (1 mol) of polyester diol (Daltorez® P720 from ICI) at 60° C.were mixed with 380 g (1 mol) of molten4,4'-methylenebis(3-chloro-2,6-diethylaniline/LONZACURE® MCDEA, LONZAAG). The following additions were then incorporated:

    ______________________________________                                        54 g (1.5 mol) of SM ®                                                                        (Bayer Leverkusen)                                          6 g of Dabco ® 1028 (Air Products)                                        2.4 g of Dabco ® solid (Air Products)                                     5 g of Dabco ® BL17 (Air Products)                                        2 g of LK221 (Air Products)                                                 ______________________________________                                    

This gives a polyol/diamine/water component with an equivalent weight of350.

Polyol Component 4

In polyol component 3, instead of 380 g (1 mol) of4,4'-methylenebis(3-chloro-2,6-diethylaniline), 570 g (1.5 mol) of thiscomponent were used. With a formulation which was otherwise identical,this gave a polyol/diamine/water mixture with an equivalent weight of330.

Polyol Component 5

2000 g (1 mol) of polytetramethylene ether glycol (Terathane® 2000 fromDu Pont) at 60° C. were mixed with 760 g (2 mol) of molten4,4'-methylenebis (3-chloro-2,6-diethylaniline). The following additionswere then incorporated:

    ______________________________________                                        90 g (2.5 mol) of SM ®                                                                        (Bayer Leverkusen)                                          9 g of Dabco ® 1028 (Air Products)                                        3.5 g of Dabco ® solid (Air Products)                                     15 g of Dabco ® BL17 (Air Products)                                       3.5 g of LK221 (Air Products)                                               ______________________________________                                    

This gives a polyol/diamine/water component with an equivalent weight of262.

Polyol Component 6 (comparison)

2000 g (1 mol) of polycaprolactone diol (Capa® 225 from Interox) at 60°C. were mixed with 180 g (2 mol) of 1,4-butanediol. The followingadditions were then incorporated:

    ______________________________________                                        13.5 g (0.75 mol) of water                                                    ______________________________________                                        6 g of Dabco ® 1028                                                                             (Air Products)                                            1 g of Dabco ® solid (Air Products)                                       5 g of Dabco ® BL17 (Air Products)                                        20 g of LK221 (Air Products)                                                ______________________________________                                    

This gives a polyol/diamine/water component with an equivalent weight of297.

Production of Test Sheets:

    ______________________________________                                        Low-pressure PU machine                                                                          Type PS 4 from LIM                                           Output: 2.5 kg/minute                                                         Component temperatures: 35° C. (prepolymer)                             50° C. (polyol component)                                             Mould temperature: 60° C.                                              Mould dimensions: 200 × 200 × 10 mm                               Processing: Casting process                                                 ______________________________________                                    

Testing after 7 days' storage under normal climatic conditions (26° C.and 50% relative humidity)

The test criteria measured was the difference (ΔDVR) in compression set,measured once at 70° C. and the second time at 80° C. Determination ofcompression set was based on DIN 53517 (specimen thickness 10 mm, 40%deformation).

Density was determined in accordance with DIN 53420.

    ______________________________________                                        Results:                                                                                 Pre-     Polyol                                                       polymer component Density                                                    Example No. No. kg/m.sup.3 .increment.DVR %                                 ______________________________________                                        1      1        1         550   3.7    Invention                                2 1 2 550 5.6 "                                                               3 2 3 500 8.0 "                                                               4 2 4 530 3.0 "                                                               5 3 5 400 4.6 "                                                               6 1 6 500 18.2 Comparison                                                   ______________________________________                                    

EXAMPLES (TDI)

Prepolymer 1

Commercially available Vibrathane® 8083 from Uniroyal (TDI prepolymerwith an NCO content of 3.4%).

Polyol Component 1

2000 g (1 mol) of polyester diol (Desmophen® 2001 from Bayer) at 60° C.were mixed with 1140 g of molten4,4'-methylenebis(3-chloro-2,6-diethylaniline/LONZACURE® MCDEA, LONZAAG). The following additions were then incorporated:

    ______________________________________                                        54.0 g (3.0 mol) of water                                                     ______________________________________                                        25 g of Dabco ® 1028                                                                            (Air Products)                                            50 g of Dabco ® Crystalline (Air Products)                                4.0 g of Dabco ® LK221E (Air Products)                                  ______________________________________                                    

This gives a polyol/diamine/water component with an equivalent weight of233.8.

Production of test sheets:

The production of the test sheets was based on the Examples (MDI).

    ______________________________________                                        Results:                                                                                 Pre-     Polyol                                                       polymer component Density                                                    Example No. No. kg/m.sup.3 .increment.DVR %                                 ______________________________________                                        1      1        1         710   1.8    Invention                              ______________________________________                                    

What is claimed is:
 1. Cellular polyurethane elastomer which can beproduced by reacting:a) an isocyanate component which includesmethylenebis(phenyl isocyanate)(MDI) and/or tolylene diisocyanate (TDI),in monomeric form or as liquefied prepolymer, with b) compounds with atleast two isocyanate-reactive hydrogen atoms, and c)4,4'-methylenebis(3-chloro-2,6-dialkylaniline) or a mixture of4,4'-methylenebis-(3-chloro-2,6-dialkylaniline) with one or morearomatic, aliphatic or cycloaliphatic diamines as chain extending agent,optionally with further polyol, and d) a blowing agent which is selectedfrom the group consisting of a blowing agent including water and awater-based blowing agent, in the presence of a catalyst and optionallyother additives.
 2. Cellular polyurethane elastomer according to claim1, wherein the chain extending agent is used together with a polyol. 3.Cellular polyurethane elastomer according to claim 1, wherein the chainextending agent used is 4,4'-methylenebis(3-chloro-2,6-diethylaniline)or a mixture of 4'4'-methylenebis(3-chloro-2,6-diethylaniline) with oneor more aromatic or aliphatic diamines.
 4. Cellular polyurethaneelastomer according to claim 1, wherein water is used as the blowingagent.
 5. Cellular polyurethane elastomer according to claim 2, whereinthe chain extending agent used in4,4'-mehtylenebis(3-chloro-2,6-diethylaniline) or a mixture of4,4'-methylenebis(3-chloro-2,6-diethylaniline) with one or more aromaticor alipathic diamines.
 6. Cellular polyurethane elastomer according toclaim 5 wherein water is used as the blowing agent.
 7. Processcomprising producing decoupling systems or moulding exposed to highdynamic and thermal stresses from the cellular polyurethane elastormerof claim
 1. 8. Process comprising producing decoupling systems andmoulding exposed to high dynamic and thermal stresses from the cellularpolyurethane elastomer of claim
 6. 9. Process for preparing cellularpolyurethane elastomer, comprising reacting:(a) an isocyanate componentwhich includes methylenebis(phenyl isocyanate)(MDI) and/or tolylenediisocyanate (TDI), in monomeric form or as liquefied prepolymer, with(b) compounds with at least two isocyanate-reactive hydrogen atoms, and(c) 4,4'-methylenebis(3-chloro-2,6-dialkylaniline) or a mixture of4,4'-methylenebis(3-chloro-2,6-dialkylaniline) with one or morearomatic, aliphatic or cyclosliphatic diamines as chain extending agent,optionally with further polyol, and (d) a blowing agent which isselected from the group consisting of a blowing agent which includeswater and a water-based blowing agent, in the presence of a catalyst andoptionally other additives.
 10. Process according to claim 7 wherein theblowing agent is present in an amount from 0.1 to 9 mols, based on 1 molof chain extender agent, and the polyol component is present in a molarratio, based on the chain extending agent, of from 0.1:1 to 10:1. 11.Process according to claim 10 wherein the reaction is conducted in acasting process in closed molds.
 12. Process according to claim 10wherein the reaction is conducted in a prepolymer process or a one-shotprocess.